Silica pigments and elastomer-silica pigment masterbatches and production processes relating thereto

ABSTRACT

Curbing of silica pigment losses and the promotion of uniformity of product in the preparation of an elastomer-silica pigment masterbatch are effected (a) by combining (1) an aqueously wet hydrated silica pigment precipitate which has a bound alkali content, which has been prepared by precipitation from an aqueous alkali metal silicate solution, and which has been continuously maintained in an aqueously wet state without drying therefrom after its precipitation, with (2) a quantity of oleophilic amine material, (3) combining the resulting treated silica pigment with an aqueous dispersion of the elastomer containing an anionic dispersing agent, with or without (4) carbon black and/or processing oil, and (5) with selected reactant-coagulant, and (b) recovering the resulting coagulum as a masterbatch, the steps prior to (b) having rendered the serum of the aqueous mixture essentially free of silica pigment. Prior to combination with the elastomer dispersion the amine treated alkaline silica pigment may be recovered as a useful dispersible alkaline silica pigment product, or the wet pigment may be treated with water soluble salt of aluminum, or zinc or the alkali earth metals and/or with water soluble mineral acid or organic acids, as well as with the said amine, and after such treatment the resulting pigment composition may be recovered as a useful dispersible silica pigment product, or the so treated wet silica pigment may be combined as in (3), (4) and (5) above, and be recovered as in (b) above in the form of a masterbatch.

United States Patent Burke, Jr. Y

[4 Oct. 24, 1972 Oliver W. Burke, Jr., 1510 SW. 13th Court, P. O. Box2266, Fort Lauderdale, Fla. 33061 22 Filed: Jan. 11,1972

21 App1.No.: 216,948

Related US. Application Data [60] Continuation-impart of Ser. No.55,384, July 16, 1970, and a continuation-in-part of Ser. No. 55,476,July 16, 1970, abandoned, which is a continuation-in-part of Ser. No.798,215, Sept. 16, 1968, abandoned, which is a division of Ser. No.611,250, Jan. 24, 1967, Pat. No. 3,523,096, which is acontinuation-in-part of Ser. No. 458,420, May 24, 1965, abandoned, and acontinuation-in-part of Ser. No. 458,379, May 24, 1965, abandoned, and acontinuationin-part of Ser. No. 479,806, Aug. 16, 1965, Pat. No.3,401,017.

[72] Inventor:

[52] US. Cl....260/33.6 AO, 106/308 N, 260/415 R, 260/415 A, 260/41.5 MP

[51] Int. Cl ..C08c 11/10, C08k 1/08 [58] Field of Search..260/33.6 A0,41.5 A, 41.5 PM, 260/41.5 R; 106/308 N [56] References Cited UNITEDSTATES PATENTS 3,392,140 7/1968 Moahs et a1. ..260/41.5 3,172,7263/1965' Burke et al. ..23/182 3,250,594 5/1966 Burke et al. ..23/1822,663,650 12/ 1953 ller 106/308 3,014,810 12/1961 Dybalski et al..106/308 2,821,232 l/l958 Wolf ..l52/330 2,607,753 8/1952 Adams..260/41 OTHER PUBLICATIONS Whitby G. 5., Synthetic Rubber, John Wiley &Sons, Inc., New York, 1954, pages 670 & 677, TS 1925 W45C.3

Morton, Maurice, Introduction to Rubber Technology, Reinhold Pub. Corp,New York, 1959, pages 169- 171 Primary ExdminerAllan Lieberman AssistantExaminer.l. H. Derrington Attorney-Hall & Houghton [5 7] ABSTRACTCurbing of silica pigment losses and the promotion of uniformity ofproduct in the preparation of an elastomer-silica pigment masterbatchare effected (a) by combining ('1') an aqueously wet hydrated silicapigment precipitate which has a bound alkali content, which has beenprepared by precipitation from an aqueous alkali metal silicatesolution, and which has been continuously maintained in an aqueously wetstate without drying therefrom after its precipitation, with (2) aquantity of oleophilic amine material, (3) combining the resultingtreated silica pigment with an aqueous dispersion of the elastomercontaining an anionic dispersing agent, with or without (4) carbon blackand/or processing oil, and (5) with selected reactant-coagulant, and (b)recovering the resulting coagulum as a masterbatch, the steps prior to(b) having rendered the serum of the aqueous mixture essentially free ofsilica pigment. Prior to combination with the elastomer dispersion theamine treated alkaline silica pigment may be recovered as a usefuldispersible alkaline silica pigment product, or the wet pigment may betreated with water soluble salt of aluminum, or zinc or the alkali earthmetals and/or with water soluble mineral acid or organic acids, as wellas with the said amine, and after such treatment the resulting pigmentcomposition may be recovered as a useful dispersible silica pigmentproduct, or the so treated wet silica pigment may be combined as in (3),(4) and (5) above, and be recovered as in (b) above in the form of amasterbatch.

12 Claims, 1 Drawing Figure Aqueously wet never dried silica pigmentprecipitate having residual alkali content Oleuphilic amine materialselected from the C to C primary, secondary, tertiary amines havingReactant from water soluble salts of aluminum and/or zinc and/or mineralacids and/or alkaline earth metals except where masterhatch includesless than 2 pts. carbon black to 3 pts.

silica by weight one or more amine grou s and having at least onehydrocarbon subetituent of 8 to 36 carbon atoms Combine (A) and w/wo (C)and/or (L) (1) Carbon black and/or (2) Processing 01'.

anionic emulsifier Aqueous dispersion of elastomcr prepared with Combine(D) and (2) then with (F) Elastomet dispexsible dry composition ofsilica pigment with oleophylic amine deposited thereon w/wo processingoil and/or carbon black Reactant from water soluble aluminum, zinc andalkaline earth metal salts and combinatlcns thereof w/wo mineral acid4M1 separation Drying of coagulum (1) Serum essentially of aqueous serumfrom cougulum free of mllicn pigment naltezbatch inccrporlt essentiallyall the si pigment employed Dry elsltcmcz-lillcl plgnont inq licePATENTED um 24 1972 Aqueously wet never dried silica pigment precipitatehaving residual alkali content Oleophilic amine material selected fromthe C to C primary, secondary, tertiary amines having one or more aminegroups and having at least one hydrocarbon substituent of 8 to 36 carbonatoms Reactant from water soluble salts of aluminum and/or zinc* and/ormineral acids *and/or alkaline earth metals except where masterbatchincludes less than 2 pts. carbon black to 3 pts.

silica by weight Combine (A) and (B) w/wo (C) and/or (L) (l) Carbonand/or 7 (2) Processing oil black Aqueous dispersion of elastomerprepared with anionic emulsifier (G) Combine (D) and (E)* then with (F)Elastomer dispersible dry composition of silica pigment with oleophylicamine deposited thereon w/wo processing oil and/or carbon black Reactantfrom water soluble aluminum, zinc and alkaline earth metal salts andcombinations thereof w/wo mineral acid Drying of coagulum coagulumMechanical separation Serum essentially of aqueous serum from free ofsilica pigment Dry elastomer-silica pigment masterbatch incorporatingessentially all the silica pigment employed SILICA PIGMENTS ANDELASTOMER-SILICA PIGMENT MASTERBATCHES AND PRODUCTION PROCESSES RELATINGTHERETO CROSS REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of copending applications Ser. No. 55,384 filedJuly 16, 1970 (Case 48DM-13) and Ser. No. 55,476 filed July 16, 1970(now abandoned), which latter application is a continuation-in-part ofapplication Ser. No. 798,215, now abandoned filed Sept. 16, 1968 as adivision of application Ser. No. 611,250, filed Jan. 24, 1967 (now US.Pat. No. 3,523,096) said application Ser. No. 611,250 having been acontinuation-in-part of earlier applications Ser. No. 458,420, filed May24, 1965 (now abandoned); Ser. No. 458,379, filed May 24, 1965 (nowabandoned); and Ser. No. 479,806, filed Aug. 16, 1965 (now US. Pat. No.3,401,017), disclosures of all of which are incorporated herein byreference. Furthermore, this application is directed to a species ofinvention that was nonelected in applicants copending application Ser.No. 55,384, and, pursuant to a restriction requirement, was withdrawnfrom consideration in that case.

BACKGROUND OF THE INVENTION 1. Field of the Invention The field to whichthis invention pertains is the preparation of dispersible silicapigments and of masterbatches from latices (i. e. aqueous dispersions)of elastomers and aqueous slurries of precipitated silica pigments.

2. Description Of The Prior Art It is well known in the art thatattempts to make masterbatches from elastomer latex and aqueouslydispersed hydrated silica pigment by latex masterbatching have resultedin loss of large amounts of the hydrated silica pigment in the motherliquor and in non-uniform masterbatches, and that even the addition oftetraethylene-pentamine (Whitby, Synthetic Rubber, John Wiley & Sons,Inc., New York, 1954, page 676) or glue, gelatin or casein (US. Pat. No.2,616,860) has not provided a satisfactory solution to this problem.Also, to applicants knowledge there is not at the present time anyelastomer-silica masterbatch being offered on the commercial market, notare the dispersible dry silica pigment compositions provided by thisinvention known.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is ablock-diagram illustrative of the process aspect of the invention.

SUMMARY OF THE INVENTION It is known to those skilled in the art toprepared hydrated silica pigment for the reinforcement of rubber byprecipitation from aqueous solutions of alkali metal silicates with theaid of carbon dioxide, and to carry out such precipitation in manners toavoid the formation of gelatinous masses(i.e. the formation of silicagel) and to promote the precipitation of a silica pigment in finelydivided form (i.e. in particles in the reinforcing size range of about0.015 to about 0.150 microns,

preferably 0.02 to 0.06 microns) and to recover the pigment from theresulting wet silica pigment by filtration, washing and drying.

The wet silica pigments formed by precipitation from 5 alkali metalsilicate solutions with the aid of carbon dioxide have a bound alkalicontent in the range of about 0.1 to 10 percentby weight as Na O, andupon being dried in this state form aggregates, from the pigmentparticles of reinforcing size, which aggregates are of much greater thanreinforcing size and will not adequately disperse (i. e. break down intoparticles of reinforcing size) when incorporated into rubber either bydry compounding or latex masterbatching.

When one treats such alkaline wet silica pigments with water solublesalts of alkaline earth metals, e. g. calcium salts, to substantiallyreplace the boundalkali metal of the silica, the resulting pigment, whendried, can still evidence the formation of aggregates of greater thanreinforcing size, which may not adequately disperse in the rubber.

When one treats the alkaline wet silica pigments with the water solublesalts of aluminum and/or zinc, to substantially replace the alkali metalcontent thereof, the resulting acidic pigment, when dried, disperses toa greater extent in rubber, evidencing less aggregation than the neutraland alkaline products referred to above.

Finally, when one renders the wet silica pigment acidic, by treatmentwith sulfuric acid or with a water soluble organic acid and drys it, theresulting acidic product is more readily dispersible in rubber, andexhibits minimum aggregation. Highly acidic pigments are not practicablefor use in the reinforcement of rubbers, since their acidity adverselyaffects vulcanization of the rubber.

Thus the drying of the wet silica pigment in alkaline, neutral, andmoderately acidic states, in each instance causes the formation ofaggregates of pigment particles to a greater or lesser degree whichaggregation can prevent adequate dispersion of the dry pigment in therubber; the formation'of these aggregates by the drying of the pigmentis irreversible; and they remain mostly as aggregates that do notdisperse in the rubber.

This invention is based on the premise that uniformity of anelastomer-pigment masterbatch depends both on obtaining incorporation ofa measured quantity of pigment in the masterbatch (e. g. avoiding lossof pigment in the serum in wet masterbatching) and adequate dispersionof the pigment in the elastomer in particles of reinforcing size (e. g.minimizing the pigment aggregation problem); and the present inventionprovides a process for accomplishing these ends by forming themasterbatch from aqueously wet hydrated silica pigment precipitateshaving a bound alkali content of 0.1 to 10 percent by weight as Na O;which has been prepared by precipitation from an aqueous solution ofalkali metal silicate with the aid of carbon dioxide; and which hascontinuously been maintained in an aqueously wet state after itsprecipitation without having been dried therefrom; and while still inthe aqeuously wet state said silica is combined with elastomerdispersion, with special provisions for avoiding loss of pigment in theaqueous phase and promoting uniformity of product in the masterbatch.

Thus, the present invention, inter alia, provides a simple and efficientprocess for the curbing of silica pigment losses and the promotion ofuniformity of product in the preparation of masterbatches of measuredsilica pigment content. As shown in the drawing, the first part of theprocess comprises the steps of:

A. providing to 100 parts by weight, dry basis, of aqueously wethydrated silica pigment precipitate which has a bound alkali contentin'the range of 0.1 to percent by weight as NagO; which has beenprepared by precipitation from an aqueous solution of alkali metalsilicate with the aid of carbon dioxide; and which has continuously beenmaintained in an aqueously wet state without having been dried therefromafter its precipitation;

B. providing a quantity of from 0.1 to percent by weight, based on thesilica pigment, dry basis, referred to in step (A), of oleophilic aminematerial, e. g. from the category consisting of the primary, secondary,and tertiary amines having at least one hydrocarbon or halohydrocarbonsubstituent containing 8 to 36 carbon atoms;

C. providing reactant material selected from the group consisting ofwater soluble acids (mineral or organic) and water soluble salts ofaluminum, zinc, or alkaline earth metals, and combinations of theforegoing; and

D. combining the wet silica pigment-from (A) with the oleophilicmaterial-from (B)-, and, optionally, with materialfrom (C)-selected fromthe group consisting of water soluble acids and water soluble'salts ofaluminum, zinc, or alkaline earth metals;

thereby to form an aqueously wet, rubber dispersible, silica pigmentcomposition. The silica pigment composition so provided may be dried toyield useful dispersible dry silica pigment compositions as indicated at(D-l or may be used without drying, e. g. in the second part of themasterbatching process, by

E. providing an aqueous dispersion containing 1. 100 parts by weight ofthe elastomer and 2. from 0.5 to 15 parts by weight of anionicdispersing agent;

G. forming a mixture of (1) the aqueous elastomer dispersion-from (E),(2) the treated wet silica pigment-from (D)-, (3) from 0-75 parts byweight of carbon black with the limitation that the total of silicapigment and carbon black, dry basis, not exceed 80 parts by weight, (4)from 0-45 parts by weight of processing oil, and (5) a sufficientquantity of the reactant material provided in step (C) to causecoagulation of the solids of the combination, whereby there is formed acoagulum of such solids rendering the aqueous serum of the combinationessentially free of silica pigment; and

H. to K. recovering the coagulum as a masterbatch.

In the optional step of combining the acid or metal salt reactant withthe silica pigment, thus lowering the alkalinity of the silica pigment,such step can be performed either simultaneously with, preceding to, or

after the combining of the silica pigment with the oleophilic amine. Theamount of acid or metal salt reactant used to treat the silica pigmentshould be no greater than that which permits the serum from theresulting masterbatch to be essentially free of silica, i. e. containsless than 2 percent by weight (dry basis) of the silica pigmentemployed. Preferably the amount of acid or metal salt reactant is atleast sufficient, though, to react at lease stoichiometrically with thealkalinity of the sil ica pigment. If too great an excess of acid iscombined with the pigment initially, the pigment can still be used inthe process of the present invention provided it is treated withsufficient alkaline material, e.g., ammonium hydroxide, to reduce theundesirable excess acid material.

When the coagulating agent employed is a mineral acid, e. g. sulfuricacid, it is preferable that it not be used in great excess over thatrequired to effect coagulation, for if it is it will tend to causesilica fines'to remain in the serum and not be incorporated in thecoagulum.

When chloroprene latex is employed with the treated or untreated silicapigment to form the masterbatch-it is preferable to use an organic acidcoagulating agent so as to form a suitable sized masterbatch crumb.

In preferred embodiments, respectively: (1) step (G) is practiced bypre-mixing the aqueous elastomer dispersion-from (E)with the treated wetsilica pigment-from (D)and then combining such mixture with the reactantmaterial referred to in step (G)- from (F); (2) in step (B) at least 0.1percent, most preferably at least 0.5 percent, based on the silicapigment referred to in step (D), dry basis, by weight of the oleophilicmaterial is provided; (3) at least 5 parts by weight of carbon black isincluded in the mixture at (D) and/or (G); and (4) at least 5 parts byweight of processing oil is included in the mixtureat (D) and/or (G).

Under the foregoing conditions the steps prior to the recovery renderthe serum resulting from the coagulation essentially free of silicapigment, thus assuring a uniform silica pigment content in themasterbatch. The achievement of this desideratum is evidenced by thefact that when the coagulum is mechanically removed from the serum asindicated at (H), the serum (1) is found to be essentially free ofsilica pigment.

The principal processes, and especially the preferred embodimentsthereof, produce pigment and masterbatch products useful for the rubberindustry.

In the making of the dispersible pigment compositions, the carbonblack-from (L)-is employed in the range of 0 to 1,500 parts per 100parts of the silica pigment, dry basis by weight, and the processingoil-from (L)-in the range of 0 to 45 parts by weight per parts of drysolids of the mixture.

In the following description of preferred embodiments, Examples l-20,23-31, and 34-38 embody the over-all process of preparing the silicacomposition and masterbatch, in which the conditions are such that anyaluminum, zinc or alkaline earth metal salt that is employed is confinedto the coagulant (F) of the drawing; Examples 1-11, 13, 21-24, 28-34,37, and 38 are of embodiments in which reactant (C) of the drawing isalso used; Examples 16-20 are of the preparation of dried, dispersiblesilica pigment compositions without using reactant (C); and Examples21-24 are of the preparation of dispersible, dry silica pigmentcompositions with reactant (C) included therein, while in Examples 28-36the masterbatches also contain carbon black and/or processing oil.Examples 37 and 38 embody preparation of an acidic silica andcoagulation of the elastomemsilica masterbatch with the aid of a watersoluble organic acid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of thepresent invention avoid the use of organic additives such astetraethylene pentamine, glue, gelatin, casein, etc., which increase thecost and may affect the curing properties of the masterbatch. Theinvention, interalia, may be used to improve wet silica masterbatchingand masterbatches using any never dried aqueously wet silica pigmentcontaining bound alkali, and is applicable to the formation ofmasterbatches therewith with elastomer latices prepared with anionicemulsifier of the type coagulable with metal salts of the coagulant. Thepresent invention does not rely for patentability on the use of laticesof elastomers which are interpolymers (i. e. graft polymers, copolymers,or block polymers) of polar vinylidene monomer of the class consistingof the primary amine, secondary amine, tertiary amine, and quaternaryammonium monomers, or which contain hydroxyl groups which uses areclaimed in separate ap plications filed concurrently herewith. It mayemploy latices of diene homopolymer rubbers such as polybutadiene,polyisoprene, polychloroprene; those of diene copolymer rubbers such asthe copolymers of diene monomers and monomers containing andcopolymerizable therewith through a single ethylenically unsaturatedgroup, e. g. butadiene-styrene, bu-

'tadiene-acrylonitrile or methacrylonitrile, butadieneacrylate ormethacrylate ester; and rubber copolymers of hydrocarbon monomers withpolar vinylidene including vinyl) monomers except those excluded above,as well as mixtures and combinations thereof with, processing oils,herein referred to as oil-rubber-silica masterbatches, and any of theforegoing further including other cooperating ingredients, such ascarbon black, providing the silica pigment comprises an essentialcomponent thereof, e. g. carbon black-elastomersilica masterbatch.

Silica pigments containing residual alkali suitable for masterbatchingin accordance with the present inven tion are usually precipitated bythe gradual acidulation of aqueous sodium silicate solution with the aidof carbon dioxide.

The oleophilic amine materials suitable for practicing the inventioninclude especially those amine compounds having one or more aminegroups, a total of from eight to 108 carbon atoms, and at least onehydrocarbon or halohydrocarbon (e. g. chlorine or fluorine containing)substituent that contains at least eight carbon atoms. Each hydrocarbonor halohydrocarbon substituent preferably has from eight to 36 carbonatoms, and may be aliphatic, cycloaliphatic or aryl. Most preferably atleast one hydrocarbon or halohydrocarbon substitutent is aliphatic(straight or branched chain, saturated or ethylenically unsaturated), e.g. alkyl. In addition to hydrocarbon and/or halohydrocarbonsubstituents, the amine may have one or more other groups containingoxygen, nitrogen, sulfur or phosphorous atoms. The following categoriesare illustrative of preferred oleophilic amines for use in the presentprocess:

1. long-chain primary monomers represented by the formula R-Nl-l inwhich R is an aliphatic hydrocarbon group of at least eight carbonatoms, e.g., is alkyl of eight to 36 carbon atoms such as octyl amine,decyl amine, dodecyl amine, tetradecyl amine, hexadecyl amine, octadecylamine, palmitoleyl amine, oleyl amine, linoleyl amine, linolenyl amine,the mixed primary amines derived from fatty oils such as coco amine,soybean amine, tallow amine, rosin amine, and partially or completelyhydrogenated amines derived from the above unsaturated amines, and thelike;

-2. long-chain secondary monoamines having at least one aliphatichydrocarbon, e. g. alkyl, substituent containing at least eight carbonatoms, e. g. long-chain secondary amines represented by the formula inwhich R contains from eight to 36 carbon atoms and R contains from oneto 36 carbon atoms, and includes but is not limited to dioctyl amine,didecyl amine, didodecyl amine, ditetradecyl amine, dihexadecyl amine,dioctadecyl amine, dipalrnitoleyl amine, dioleyl amine, dilinoleylamine, dilinolenyl amine, the mixed secondary amines derived from fattyoilssuch as dicoco amine, disoybean amine, ditallow amine, hydrogentatedditallow amine, N-methyloctylamine, N-methyldodecylamine,N-methylhexadecylamine, N-ethyloctylamine, N-ethyloctadecylamine,N-propyldodecylamine, N-butyloctylamine, and the like;

3. long-chain tertiary monoamines having at least one aliphatichydrocarbon, e. g. alkyl, substituent containing at least eight carbonatoms, e. g. (a) long chain, acyclic tertiary amines represented by theformula in which R contains eight to 36 carbon atoms, R contains one to36 carbon atoms and R" contains one to 36'carbon atoms, including butnot limited to trioctyl amine, tridodecyl amine, tristearyl amine,octyldimethyl amine, dioctyl methyl amine, dodecyl dimethyl amine,didodecyl methyl amine, octadecyl dimethyl amine, dioctadecyl methylamine, the mixed tertiary amines derived from fatty oils, coco dimethylamine, dicoco methyl amine, soybean dimethyl amine, disoybean methylamine, tallow dimethyl amine, ditallow methyl amine, and thehydrogenated or partially hydrogenated products of unsaturated tertiaryamines, and the like; and

b. long chain cyclic tertiary amines including but not limited to N-cocomorpholine, N-soya morpholine, N-tallow morpholine and the like;

4. long-chain diamines and polyamines having at least one aliphatichydrocarbon, e.g., alkyl, substituent containing at least eight carbonatoms, e. g. from eight to 36 carbon atoms, including, but not limitedto, the diamines represented by the formula RNH(CH )1NH in which R is analiphatic hydrocarbon group of eight to 36 carbon atoms and x is aninteger from 1 to 18, as for example N-coco-trimethylene diamine, N-soyatrimethylene diamine, N-tallow trimethylene diamine, N-oleyltrimethylene diamine, N-octyl dimethylene diamine, N-octyltetrarnethylene diamine, the above diamines with one or more aminehydrogens replaced by a methyl, ethyl, propyl or butyl group, and thelike;

'5. long-chain, polyalkoxylated, secondary and tertiary monoaminescontaining at least one aliphatic hydrocarbon, e.g., alkyl, substituenthaving at least eight carbon atoms, e.g., from eight to 36 carbon atoms,including but not limited to, the polyethoxylated and polypropoxylatedamines represented by the formulas in which R is an aliphatichydrocarbon group of eight to 36 carbon atoms, R is an aliphatichydrocarbon group of one to 36 carbon atoms, and x x x x y,, and y areeach integers between 1 and 30, and including but not limited to cocoamine, soybean amine, tallow amine and stearyl amine each reacted with aplurality, e. g. 2, 5, or 15, moles of ethylene oxide or propylene oxideper mole of amine, and the like;

6. long-chain, polyalkoxylated diamines having at least one aliphatichydrocarbon, e.g., alkyl, substituent of at least eight carbon atoms,e.g., from eight to 36 carbon atoms, including, but not limited to, thediamines represented by the formulas in which R is an aliphatichydrocarbon group of eight to 36 carbon atoms and x x y y 2 and 2 areeach integers between 1 and 30, which include, but are not limited to,the reaction products of N-coco trimethylene diamine, N-soyatrimethylene diamine and N-tallow trimethylene diarnine each with aplurality of, e. g. 3, 10 or moles of ethylene oxide or propylene oxideper mole of amine, and mixtures of such oxides and the like.

The oleophilic amine if desired can be applied to the wet silica pigmentwhile the amine is in solution in a suitable organic solvent, e.g.,isopropanol, hexane, benzene or toluene. This facilities evendistribution of the amine throughout the pigment.

It is understood that the process of the present invention does notencompass the preparation of the aminetreated silica pigment by addingto the pigment either an oleophilic quarternary ammonium compound or anoleophilic-amine salt of a carboxylic acid, elsewhere claimed.

Carbon Black Processing Oils The term fprocessing oils as used hereinmeans rubber processing material of both liquid and solid types (ifrequired the solids types can be converted to the liquid state for useherein with the aid of solvent or plasticizer) and includes theprocessing materials set forth under Plasticers and Softeners at pages149 to 214 of the publication entitled Materials and CompoundingIngredients for Rubber, compiled by]. V. Del Gatto, published by RubberWorld, 1968, and herein incorporated by reference and among the types ofprocessing materials especially suitable for use in this invention are(a) the coal tar oils and pitches e.g., Bardol (TM), Bardol B (TM); .(b)the asphalts, e. g. BRH No. 2 (TM); (c) the petroleum oils including theparafiinic, naphthenic, aromatic, and highly aromatic categories, whichare commercially available under trademark designations, Sunpar (TM),Sundex (TM), Sunthene (TM), Circosol (TM), and Shellflux (TM) oils, andthe like, such as Circosol 2XH (TM), Sundex 53 (TM), Shell SPX 97 (TM),Dutrex-20, 419, 726, 757, 787 (TM), and Califlux TI (TM) and other oilssuitable for rubber compounding or the oilextension of synthetic rubber;(d) the coumarone-indene oils and resins, e. g. Cumar Resin RH, -P10, T(TM); (e) the liquid ester type plasticizers, e. g. dibutyl phthalate,di- (2-ethylhexyl) phthalate, diglycol laurate, dibenzyl sebacate,tributoxyethyl phosphate, tricresyl phosphate and the like; (f) thephenol formaldehyde thermoplastic resins, e. g. Durez 12687, 12707 (TM)and the like; (g) the hydrocarbon resins, e. g. Neville-LX 782, LX 125,(TM), Para-Flux, Para Resin 2457 (TM); (h) the coumarone-indene resinpolymers, e. g. Picco Resins (TM); (i) the pine tars and pine tar oils,rosin and rosin oils, and tall oil and its derivatives, e.g., PT-lOl,P1401, PT800 (TM); and the like.

The term water soluble acids means water soluble mineral acids and watersoluble organic acids. The water soluble mineral acids include sulfuricacid, hydrochloric acid, and the like. The water soluble organic acidsinclude, but are not limited to, the water soluble, aliphaticmonocarboxylic acids, e.g., the alkanoic acids of one to three carbonatoms, (formic,

- acetic, and propanoic) and the water soluble, hydroxylalkanoic acidssuch as hydroxyacetic acid, Z-hydroxypropanoic acid, 3-hydroxypropanoicacid, the hydroxybutanoic acids, 2,3-dihydroxypropanoic acid, and thelike.

EXAMPLES The following examples will serve to illustrate the inventionin more detail:

Silica Preparation The aqueously wet never dried alkaline silica pigmentemployed in all the examples was prepared in a manner similar to Example9 of US. Pat. No. 3,250,594 except that the ratio of 41 Be commercialsodium silicate (Na O/(SiO to water was approximately 1 to 4.5 byweight. The carbon dioxide was supplied to the sodium silicate with theaid of a single submerged combustion burner up to the appearance of theTyndall effect and with two such burners thereafter. The use of thesubmerged combustion burners was according to U.S. Pat. No. 3,372,046.The silica product was filtered and washed to reduce the soluble saltsto the range of 1 to 2 percent and the filter cake had a solids ofapproximately percent by weight. The resulting aqueously wet silicapigment was designated wet alkaline silica pigment-l, and had a boundand residual alkali content of about 1.5 percent by weight as Na O, anda serum pH of about 8.5 (8.5 to 9.5 or even higher).

A portion of this alkaline silica filter cake was slurried with about ahalf volume of water and was acidified to a pH of 4.5 with dilutesulfuric acid and as a filter cake, with washing to a filtrate pH ofabout 6.4 to 7.0, had a solids of approximately 10 percent by weight.The resulting aqueously wet silica slurry was designated wet silicapigment-ll.

The just described filter cakes having a solids content of about 10percent by weight are embraced within the term wet silica pigment (whichherein connotes aqueously wet silica pigment) as are wet pigments ofmore reduced water content, which can be prepared by pressing the saidfilter 'cakes, or of augmented water content, e. g. slurries having lessthan 10 percent solids content, and the terms aqueously wet silicapigment or aqueously wet state, as employed herein are generic toallsuch conditions. Thus these terms as employed herein embraceaqueously wet silica pigment materials having a solids content in therange of about 1 percent to about 65 percent solids, dry basis, byweight; however, for economy in the practice of the invention wet silicapigments of reduced water content (solids content 8 percent or higher)are preferred.

To determine pigment quality a portion of wet silica pigment-H was driedat 105 C., micro-pulverized and compounded as set forth in Table Ihereof.

Cumar Resin RH, a trademark poduct of Allied Chemical Corp.

. The compound was aged over-night, re-milled and cured for 45 minutesat 287 F.

The physical test data for the vulcanizate so prepared with theforegoing silica pigment is set forth in Table II hereof.

In addition to the procedures set forth in the Tables it has also beenfound that streams of the elastomer latex and of the amine treatedsilica pigment slurry may be continuously mixed and that the resultingstream may be continuously mixed with a stream of the coagulant, andthat this procedure also will yield a coagulum containing essentiallyall of the silica pigment, leaving essentially no silica pigment in theaqueous phase. Thus the processes of the examples are adaptable foreither continuous or batch production of the masterbatch. In thoseinstances in which an-oil-rubber-silica pigment masterbatch is desired,up to about 30 percent of oil based on the elastomer is added'to thelatex prepared with anionic emulsifier according to the foregoingexamples, preferably with a small amount of ammonium hydroxide to aiddispersion of the oil into the elastomer, and it will thus be understoodthat the masterbatch and elastomer dispersion contemplated by theinvention may contain a minor proportion of oil. Similarly in Examples 1to 11, any soluble aluminum salt may be substituted for the hydratedaluminum sulfate, e. g., aluminum ammonium sulfate or aluminum sodiumsulfate, and the coagulant solution contemplated by the invention maythus comprise minor amounts of ammonium and/or alkali metal saltswithout detriment to the process. Furthermore the elastomer latex and/orthe treated dispersion of silica pigment and/or the aqueous coagulantsolution may contain a small proportion of ammonium hydroxide whichappears in certain instances to facilitate the practice of theinvention. When the coagulant solution contains mineral acid a quantityof aqueous sodium chloride may advantageously be employed therewith toavoid the necessity of having to use excessive quantities of the acid toeffect coagulation, as an excessive quantity of such acid may causesilica pigment to appear in the serum. When carbon black is also to beincluded in the elastomer-silica pigment masterbatch, it may, ifdesired, be incorporated as an aqueous slurry along with the slurry ofthe silica pigment.

In the following tabulations of Examples l--38 the ingredients (A), (B),(C) etc., are listed in the order of their addition, except whereotherwise specifically set forth. These examples were carried out atambient temperatures, however, more elevated temperatures may beemployed, e. g. to accelerate the processing.

TABLE III Polymer-silica Masterbatch (Parts by wt.)

(pl-l 8.5-9.5)

Dry solid: basis 15 15 15 v 15 Water 50 5O 50 50 (B) Reagent-AqueousSolution 10% sulfuric acid 5.1 5.1 5.1 5.1 Silica slurry, pH 6.4-7.0 (X)X X X X Water 10 10 l 10 filter cake after washing (C) Oleophilic AmineMaterial in lsopropanol 10% Armeen T" 3.0 IOpercent Ethoduomeen T/25 1.510% Duomeen 'l 3.0 3.0 (D) Polymer Latex Butadiene-styrene 153 153 153150 Dry solids basis 30 30 30 30 Antioxidant 0.6 0.6 0.6 0.6 (E)Coagulant-Aqueous Solution 2% aluminumsulfate 90 80 90 54 2% sulfuricacid 12 Water 450 (F) Coagulation Added treated silica polymer latex to1 coagulant (X) X X X X pl-l serum 4.0 4.0 4.0 4.0 Silica in serumnonenone none none (G) Masterbatch Filtered and washed (X) X X X XDried(lO5C.) (X) X X X X Armeen-T tallow-amine, a trademark product.

Eth'oduomeen T/25 Polyoxycthylene tallow trimethylenc diamine, a

trademark product.

"Duomeen T N-tallow trimethylene diamine, a trademark product.

"Antioxidant is 2,2'-methylene-bis(4-methyl-6-t.-butylphenol) and may beadded as a solvent solution e.g. dissolved in isopropanol or as TABLE IVPolymer-silica Masterbatch (Parts by wt.) Example 5 6 7 (A) SilicaPigment Slurry Alkaline silica pigment-l (pH 8.5-9.5) 150 150 150 150Dry solids basis 15 15 15 15 Water 50 50 S0 50 (B) Reagent-AqueousSolution 10% sulfuric acid 5.1 5.1 5.1 5.1 Silica slurry pH 6.4-7.0 (X)X X X X Water 10 10 l0 l0 filter cake after washing (C) Oleophilic AmineMaterial in lsopropanol 10% Armeen DMCD 1.5 10% Armeen ZC 3.0 10%Ethomeen T/l2 115 10% Dehydroabietylamine 1.5 (D) Polymer LatexButadiene-styrene 153 153 153 153 Dry solids basis 30 30 30 30Antioxidant 0.6 0.6 0.6 0.6 (E) coagulant-Aqueous Solution 2% aluminumsulfate 70 60 70 60 Water 250 250 250 250 (F) Coagulation Addedcoagulant to treated Silica polymer latex (X) X X X X pH serum 4.0 4.04.0 4.0 Silica in serum nonenone none none (G) Masterbatch Filtered andwashed (X) X X X X Dried (105C.) (X) X X X X "EthomeenTll2-di(polyoxyethylene) tallow amine, a trade-mark product. "S811 1502(T. S.- 19.7%).

"Antioxiclant is 2,2'-methylene-bls(4--methyl-6-t.-butylphenol'Aluminurn sulfate AI,(SO 14H,O.

TABLE V Polymer-Silica Masterbatch (Parts by wt.) Example 9 l0 l l (A)Silica Pigment Slurry Alkaline Silica pigment-l (pl-1 8.5-9.5) 150 150150 Dry solids basis 1 5 1'5 15 Water 50 50 50 (B) Reagent-AqueousSolution 2% sulfuric acid 25.5 25.5 25.5 Silica slurry'pl-l" 7 7 7 Water60 90 *filter cake after washing (C) Oleophilic Amine Material inlsopropariol 10% Duomeen 1*" 1.5 3.0 3.0 (D) Polymer LatexButadiene-acrylonitrile"'" 63 Butadiene-acrylonitrile 61 Chloroprene 43Dry solids basis 25 g 25 25 Antioxidant" 0.5 0.5 0.5 Water 60 60 150 (E)coagulant-Aqueous Solution 2% aluminum sulfate 90 70 Water 250lsopropanol 75 (F) Coagulation Treated silica polymer latex were addedto coagulant (X) X X X pH serum 4.0 4.0 4.0 Silica in serum none nonenone (6) Masterbatch Filtered and washed (X) X X X Dried.(l05C.) (X) X XX Duomeen T, N-tallow trimethylene diamine, a trademark product. l-lycar1570 X 20, a carboxyl-modified butadiene/acrylonitrile latex, atrademark product.

"'Hycar 1561, a butadiene/acrylonitrile latex, a trademark product.*Chloroprene Neoprene 635 latex, a trademark product. ""Antioxidant is2,2'-methylene-bis (4-methyl-6-t.-butylphenol). Aluminum sulfate Al,(SO1 411,0.

TABLE VI Polymer-Silica Masterbatch (Parts by wt.)

Example 12 13 14 15 (A) Silica Pigment Slurry Alkaline silica pigment-l(pH 8.5-9.5) 150 150 150 150 Dry solids basis 15 l5 l5 15 Water 60 5O 5050 (B) Reagent-Aqueous Solution 2% sulfuric acid 25.5 2% aluminumsulfate" 50 2% zinc sulfate 42 Silica slurry pH 7.0 4.0 7.0 Water 60 6060 filter cake after washing (C) Oleophilic Amine Material inlsopropanol 10% Duomeen T 3.0 3.0 3.0 3.0 (D) Polymer LatexButadiene-styrene 153 153 153 153 Dry solids basis 30 30 30 30Antioxidant 0.6 0.6 0.6 0. (E) coagulant-Aqueous Solution 2% zincsulfate 180 2% calcium chloride 9 2% magnesium sulfate 1% bariumchloride 130 Water 160 130 (F) Coagulation XX XX '"Aluminum sulfateAl,(S0.),.l4l-1,0.

"Duomeen T, N-tallow trimethylene diamine, a trademark product. ""SBR1502 (T. S.= 19.7%).

*Antioxidant is 2,2'-urethylene-bls(4-methyl-6-t.-butylphenol).

TABLE vn Dispersible Silica (Parts by wt.)

Example 16 17 20 (A) Silica Slurry Alkaline silica pigment-l (pH8.5-9.5) Dry solids basis Water (13) Oleophilic Amine Material inlsopropanol 10% Armeen T 10% Ethoduomeen T/25 10% Duomeen T 10% Stearylamine sulfate 10% Oleyl amine hydrochloride (C) Treated Silica Dried(105C. (X)

'Armeen-T tallow amine, a trademark product.

Ethoduomeen T/25 Polyoxyethylene tallow triethylenediamine, a trademarkproduct.

"Duomeen T N-alkyl trimethylene diamine, a trademark product.

Incorporated with the aid ofWaring blender, a tradrnark product.

TABLE VIII Dispersible Silica (Parts by wt.)

Example 21 22 24 (A) Silica Slurry Alkaline silica pigment-l (pH8.5-9.5) Dry solids basis Water (B) Reagent Aqueous Solution 2% aluminumsulfate 2% zinc sulfate 2% sulfuric acid 20% acetic acid Silica slurry,pH (C) Oleophilic Amine Material in Isopropanol Arrneen DMCD 10% Armeen2C 10% Etho rneen T/12 10% Armeen T (D) Treated Silica Dried (105C.) (X)Glll TABLE IX Polymer-Silica Masterbatch (parts by wt.)

Example 25 26 27 (A) Silica Pigment Slurry Alkaline silica pigment -l125 125 Dry solids basis 12.5 12.5 12.5

Water 50, 50 50 (B) Oleophilic Amine Material 10% Duomeen T" 1.5 1.5 3.0(C) Combine (A) and (B) Blend (X) X X X (D) Polymer Latex-Aqueous 39.8%Butadiene-acrylonitrile 63 41% Butadiene-acrylonitrile" 61 58%Chloroprene 43 Dry solids basis 25 25 25 Antioxidant 0.5 0.5 0.5

Water 290 430 150 (E) coagulant-Aqueous Solution 2% Aluminum sulfate" l15 l 10 pH 4.5 4.5 4.5 (F) Combine (C) and (D) then add to (D) Blend andfilter (X) I X X g X Silica in aqueous phase none none none (G)Masterbatch Dried (105C.) (X) X X X (1)A trademark product, isopropanol."Hycar l570 X 20, a trademark product which is a carboxyl-modifiedN-tallow trimethylene diamine in butadiene/acrylonitrile latex.

The level of amine employed in the foregoing Examples 1 to 15 and 25 to27, of the order of 1-3 percent is sufficient to render the serum of themasterbatch essentially free of silica pigment. Vulcanizates preparedfrom the masterbatches so provided have improved tensile strength andonly slightly decreased modulusas compared with similar Vulcanizatesprepared by dry milling. However, if the quantity of oleophilic aminematerial is increased significantly above the order of 1 percent basedon the silica, by weight, e. g. into the range of 2 to 20 percent dryweight based on the silica, then the modulus of the Vulcanizates of themasterbatches is reduced.

With respect to a further aspect of the invention, it is well known thatif a silica pigment precipitated from an alkali metal silicate solutionwith the aid of carbon dioxide is dried in the alkaline state, itagglomerates to hard lumps which even after grinding do not uniformlydisperse in rubber compositions. For this reason it has been thepractice to render such silica pigment precipitates acidic, or at leastneutral, e. g. by treat ment with mineral acid or organic acids beforedrying the same, in order to render them dispersible. The presentinvention, as shown in Examples 16 to 20, has disclosed that suchpractice, and its disadvantages, can be obviated, and that a rubberdispersible dry alkaline silica pigment can be prepared, by treating theslurry of alkaline silica pigment precipitate with oleophilic aminematerial and then drying the same. The invention has further disclosedthat when such amine is employed in sufiicient quantity to render thedry silica pigment dispersible in dry rubber, and not significantly inexcess of such quantity, the resulting dispersible all kaline dry silicapigment is useful for imparting high modulus to vulcanizate in which itis employed in normal compounding proportions. The invention has stillfurther disclosed that by employing augmented amounts ofv such amine,significantly in excess of those which render the silica dispersible, adry alkaline silica pigment may be obtained which is readilydispersible, and which does not itself impart high modulus to thestocks, but which does impart an improved balance of tensile strengthand tear or abrasion resistance to the vulcanizate. And in thisconnection, the invention has further disclosed that a vulcanizatecombining high modulus, high tensile strength and high tear or abrasionresistance, can be provided by employing a combination' of dry alkalinesilica pigment hearing such aug mented amounts of such amine, togetherwith other reinforcing fillers, e. g. carbon black, acidic silicapigments, and dry silica pigments having less than such augmentedamounts of the oleophilic amine material.

Also the invention has disclosed that when, as in Examples 21 to 24, thealkaline silica pigment is treated with both the oleophilic aminematerial and with reactants selected from the class consisting of watersoluble mineral and organic acids, water soluble salts of alkaline earthmetals, aluminum or ainc, and combination. of the foregoing, thendispersible dry alkaline, neutral or acidic silica pigments areobtainable suitable for rubber compounding, and that by use of augmentedquantities of such amine, as aforesaid, such pigments are enabled toimpart improved tear resistance to vulcanizates prepared therewith asabove described.

EXAMPLES 28-36 Polymer-silica masterbatches may also be preparedcontaining processing oils and/or carbon black as previously describedto obtain oil and/or carbon black containing elastomer-silica pigmentmasterbatches, without departing from the invention. In such practice,from 0 to ,65 parts by weight of carbon black may be employed (with thelimitation that .the total quantity of treated pigment and carbon black,dry basis, not exceed 80 parts by weight, per 100 parts of theelastomers) and/or from 0 to 45 parts by weight of processing oil may beemployed, by combining with the elastomer latex and silica pigmentslurry prior to the coagulation thereof by the aqueous coagulant as setforth in the drawing. Such combinations may be effected in any suitableway, e. g. the carbon black may be added as an aqueous slurry and theprocessing oil as an aqueous dispersion preferably with an anionicand/or nonionic emulsifying agent and/or ammonium hydroxide.

In preferred embodiments of this invention, the oleophilic amine treatedwet silica pigment beingin a slurry form, the carbonblack,.and/or'processing oil may be added directlyto-the said slurrywithout any prior aqueous dispersment, e. g. with the aid of a highshear mixer, such as a Waring blender to obtain a uniform dispersion ofthe combination.

The following Examples 28-38 are illustrative of such modes ofpracticing the invention.

Example 29 so (A) Silic'a Pigment Slurry Alkaline silica pigment-l (pH8.5-9.5) Dry basis Water (8) Reagent-Aqueous Solution 2% Sulfuric acid(C) Combine (A) and (B) Blend, filter and wash (X) Silica pH 6.4-7.0 (X)(D) Oleophilic Amine Material in Benzene 5% Stearylamine" 20%dicoco-amine 20% rosin amine (E) Combine (C) and (D) (F) Carbon BlackStatex 160" Philblack 0 Thermax (G) Processing Oil Sundex 2 X H I (H)Combine (E), (F) and (G) (X) (l) Other Ingredients Water (J) Add (l) toBlender, then (H) Blender", min. (K) Polymer Latex Butadiene-styrene Drysolids basis 4 Antioxidant (L) Coagulant 2% aluminum sulfate" 2% zincsulfate 2% calcium chloride 2% sulfuric acid (M) Combine (J) (K) then(L) Blend, (X) Serum pl-l Silica and/or black in serum (N) MasterbatchFilter and wash (X) Dried (C) (X) X Ill ll- X X X 4.0 6.4 6.5 3.5

nonenone XX XX TABLE XI Polymer-Silica Masterbatch Including CarbonBlack (Parts by wt.) Example 32 33 (A) Si ica Pigment Slurry Alkalinesilica pigment -l (PH 8.5-9.5) Dry solids basis (B) Reagent-AqueousSolution 2% aluminum sulfate" 2% calcium chloride 2% magnesium sulfateWater (C) Oleophilic Amine Material 20% Rosin amine" I Cocoamine 20%Dicocoamine" N-tallow-l ,3- propylene diamine reacted with ethyleneoxide (D) Combine (A) and (B) then (C) Blend, min. (B) Carbon BlackThermax" Philblack 0"" (F) Combine (D) 8: (E)

Blend, min. (G) Polymer Latex Polychloroprene ButadieneacrylonitrileButadienestyrene Dry basis Antioxidant Water lsopropanol (coagulatingaid) (H) Combine (F) and (X) (l) Coagulant-Aqueous Solution 2% Calciumchloride 2% Magnesium sulfate 2% Aluminum sulfate 2% Sulfuric acid 12%Sodium chloride (J) Combine (H) and (l) Blend, (X) Serum pH Silicaand/or black in serum (K) Masterbatch Filter and Wash (X) Dried (105C.)(X) LII XX XX "Aluminum sulfate AI,(SO,),.14H,O.

"'Rosin Amine D. (a trademark product) in benzene.

Armeen C (a trademark product) 'Arrneen 2C (a trademark product) inbenzene.

""Ethoduomeen T-25 (a trademark product) containing 15 moles of ethyleneoxide per mole of diamine.

"Waring blender (a trademark product).

"Trademark product.

"Neoprene 635 (58% solids latex), a trademark product.

l-lycar 15 61 (41% solids latex), a trademark product.

SBR-1502 (18.4% solids latex).

"Antioxidant is 2,2-methylene-bis(4-methylene-6-t.hutylphenol). Thecombining was through a mixing nozzle; serum pH was 4 and serum wasdevoid of silica and carbon black.

Premixed with the water.

(G) Polymer Latex Polychloroprene 52 5 2 Dry basis 30 30 Antioxidant 0.60.6 Water 52' 150 50% Aqueous isopropanol(coagulating aid) (H) Combine(F) and (G) Blend yi) x) Silica and/or black in serum none (l) Coagulant2% Aqueous acetic acid 40 lsopropanol 200 Water 100 (J) Combine (H) and(l) Blend. (X) X Silica and/or black in serum none (K) MasterbatchFilter and wash (X) X X Dried (C.) (X) X Y X "Rosin Amine D (a trademarkproduct) "Trademark product. ""Waring blender. Neoprene 635 (58% solidslatex), a trademark product. Antioxidant is2,2'-methylene-bis(4-methylene-6-t.-butylphenol). Concurrently feed (F)and (G) together and coagulation takes place to form masterbatch.

The masterbatches prepared in accordance with the present invention maybe compounded with vulcanizing ingredients and vulcanized by anysuitable recipe (e. g. the recipe set forth in Table I, above) to formuseful vulcanizates.

From the foregoing disclosure, it will be appreciated, inter alia, thatthe present invention improves elastomer-silica pigment masterbatches byemploying silica pigments combined with specified materials.

In certain co-pending applications filed on July 16, 1970 differentmodes of improving elastomer-silica pigment masterbatches are providedby employing elastomers supplied with certain substituent groupsimproving the ability of the elastomers to be latex masterbatched withthe aqueously wet silica pigments.

To maintain clear lines of division between the copending applications,the claims of this application recite, and rely for patentability on,only its own improvements, without prejudice to their applicability toprocesses or products-employing such improvements along with a differentimprovement disclosed in one of said co-pending applications.

Also, while there have been described herein what are at presentconsidered preferred embodiments of the invention, it will be obvious tothose skilled in the art that modifications and changes may be madetherein without departing from the essence of the invention. It istherefore understood that the exemplary embodiments are illustrative andnot restrictive of the invention, the scope of which is defined in theappended claims, and that all modifications that come within the meaningand range of equivalents of the claims are intended to be includedtherein.

I claim:

1 A process for the curbing of silica pigment losses and the promotionof uniformity of product in the preparation of a silicapigment-elastomer masterbatch from a. aqueously wet, hydrated silicapigment which has a bound alkali content, calculated as Na o, in therange of 0.1 to 10 percent by weight, dry basis, and which has beenprepared by precipitation from an aqueous solution of sodium silicatewith the aid of carbon dioxide, followed by filtering and washing, andwhich has been continuously maintained in an aqueously wet state afterits precipitation, and

b. an aqueous dispersion of rubbery addition polymer of ethylenicallyunsaturated monomer of two to 20 carbon atoms, said dispersioncontaining, for each 100 parts by weight of said polymer, from 0.5 to 15parts by weight of anionic dispersing agent for the polymer, whichmethod comprises the following steps:

. combining said wet pigment with from 0.1 to 20 percent, based on thedry weightof the silica pigment, of oleophilic amine having at least onehydrocarbon or halohydrocarbon substituent that contains at least eightcarbon atoms, thereby providing an amine-treated, wet pigment,

2. mixing together (i) said amine-treated, wet pigment, (ii) asufficient amount of said aqueous dispersion of rubbery polymer toprovide from five to 75 parts of said pigment (calculated on the basisof thedry weight of the pigment prior to the amine treatment) for each100 parts by weight of said polymer, (iii) from.0 to 65 parts, for each100 parts by weight of said polymer, of carbon black, with thelimitation that the total of said silica pigment and carbon black, drybasis, not exceed 80 parts per each 100 parts by weight of said polymer,(iv) from to 45 parts, for each 100 parts by weight of said polymer, ofprocessing oil, and (v) sufficient coagulating agent selected from thegroup consisting of water soluble acids and water soluble aluminum,zinc, and alkaline earth metal salts to cause coagulation of the solidsof the mix, thereby providing a silica pigment-elastomer coagulum in anaqueous serum that is essentially free of silica pigment, and

3. recovering said coagulum as a masterbatch.

2. The process of claim 1, wherein the aqueously wet, alkaline silicapigment,- prior to being combined in step (1) with said oleophilicamine, is combined with reactant selected from the group consisting ofwater soluble acids, water soluble aluminum, zinc, and alkaline earthmetal salts, and combinations of the foregoing to lower the alkalinecontent of the silica pigment.

3. The process of claim 1, wherein the aqueously wet, alkaline silicapigment, while being combined in step (1) with said oleophilic amine, isalso combined with reactant selected from the group consisting of watersoluble acids, water soluble aluminum, zinc, and alkaline earth metalsalts, and combinations of the foregoing to lower the alkaline contentof the silica pigment.

4. The process of claim 1, wherein step (2) is per formed by combiningthe amine-treated pigment with at least a portion of the coagulatingagent, so as to lower the alkaline content of the silica pigment, beforecombining the pigment with the aqueous polymer dispersion. z i

5. A process as claimed in claim 1, in which step (2) is performed bypre-mixing theaqueous dispersion of polymer with the amine-treated wetsilica pigment, and thereafter combining such mixture with thecoagulating agent.

6. A process as claimed in claim 5, in which the combining of themixtureof aqueous dispersion of polymer and amine-treated wet silica pigmentwith the coagulating agent is efiected by adding said mixture to an aquep r e 3 8% a fie c i i n iq i wherein the quantity of amine used instep (1) is at least 0.5 percent by weight, based on the dry weight ofthe silica pigment.

8. A process as claimed in claim 1, wherein at least 5 parts by weightof the carbon black, for each 100 parts amine contains eight to 108carbon atoms.

12. A process as claimed in claim 11, wherein the I amine contains atleast one aliphatic hydrocarbon substituent having at least eight carbonatoms, and no substituents having more than 36 carbon atoms.

2. The process of claim 1, wherein the aqueously wet, alkaline silicapigment, prior to being combined in step (1) with said oleophilic amine,is combined with reactant selected from the group consisting of watersoluble acids, water soluble aluminum, zinc, and alkaline earth metalsalts, and combinations of the foregoing to lower the alkaline contentof the silica pigment.
 2. mixing together (i) said amine-treated, wetpigment, (ii) a sufficient amount of said aqueous dispersion of rubberypolymer to provide from five to 75 parts of said pigment (calculated onthe basis of the dry weight of the pigment prior to the amine treatment)for each 100 parts by weight of said polymer, (iii) from 0 to 65 parts,for each 100 parts by weight of said polymer, of carbon black, with thelimitation that the total of said silica pigment and carbon black, drybasis, not exceed 80 parts per each 100 parts by weight of said polymer,(iv) from 0 to 45 parts, for each 100 parts by weight of said polymer,of processing oil, and (v) sufficient coagulating agent selected fromthe group consisting of water soluble acids and water soluble aluminum,zinc, and alkaline earth metal salts to cause coagulation of the solidsof the mix, thereby providing a silica pigment-elastomer coagulum in anaqueous serum that is essentially free of silica pigment, and 3.recovering said coagulum as a masterbatch.
 3. The process of claim 1,wherein the aqueously wet, alkaline silica pigment, while being combinedin step (1) with said oleophilic amine, is also combined with reactantselected from the group consisting of water soluble acids, water solublealuminum, zinc, and alkaline earth metal salts, and combinations of thEforegoing to lower the alkaline content of the silica pigment.
 4. Theprocess of claim 1, wherein step (2) is performed by combining theamine-treated pigment with at least a portion of the coagulating agent,so as to lower the alkaline content of the silica pigment, beforecombining the pigment with the aqueous polymer dispersion.
 5. A processas claimed in claim 1, in which step (2) is performed by pre-mixing theaqueous dispersion of polymer with the amine-treated wet silica pigment,and thereafter combining such mixture with the coagulating agent.
 6. Aprocess as claimed in claim 5, in which the combining of the mixture ofaqueous dispersion of polymer and amine-treated wet silica pigment withthe coagulating agent is effected by adding said mixture to an aqueoussolution of the coagulating agent.
 7. A process as claimed in claim 1,wherein the quantity of amine used in step (1) is at least 0.5 percentby weight, based on the dry weight of the silica pigment.
 8. A processas claimed in claim 1, wherein at least 5 parts by weight of the carbonblack, for each 100 parts of polymer, is used in step (2).
 9. A processas claimed in claim 1, wherein at least 5 parts by weight of processingoil, for each 100 parts of polymer, is used in step (2).
 10. A processas claimed in claim 8, wherein at least 5 parts by weight of processingoil, for each 100 parts of polymer, is used in step (2).
 11. A processas claimed in claim 1, wherein the amine contains eight to 108 carbonatoms.
 12. A process as claimed in claim 11, wherein the amine containsat least one aliphatic hydrocarbon substituent having at least eightcarbon atoms, and no substituents having more than 36 carbon atoms.